The sensitivity of sunflower (Helianthus annuus L.) plants to UV-B radiation is altered by nitrogen status

Abstract

Interaction effects between nitrogen and UV-B radiation were studied in sunflower (Helianthus annuus L. variety IAC-Iarama) plants grown in a greenhouse under natural photoperiod conditions. Plants were irradiated with 0.8W m-2 (control) or 8.0W m-2 (+UV-B) of UV-B radiation for 7h per day. The plants were grown in pots containing vermiculite and watered with 70% of full strength nitrogen-free Long Ashton solution, containing either low (42.3ppm) or high (282ppm) nitrogen as ammonium nitrate. High nitrogen increased dry matter of stem, leaves and shoot, photosynthetic pigments and photosynthesis (A) without any alteration in stomatal conductance (gs) nor transpiration (E) while it reduced the intercellular CO2 (Ci) concentration, and malondialdehyde (MDA) content. High UV-B radiation had negative effects on dry matter production, A, gs and E with the effects more marked under high nitrogen, whereas it increased Ci under high nitrogen. Activity of PG-POD was reduced by high UV-B radiation under low nitrogen but it was not changed under high nitrogen. The UV-B radiation increased the MDA content independently of nitrogen level. Results indicate that the effects of UV-B radiation on sunflower plants are dependent of nitrogen supply with high nitrogen making their physiological processes more sensitive to UV-B radiation.

Effects of Ultraviolet-B Radiation in Plant Physiology

“…These impairments lead to the reductions in plant height, dry weight, leaf area, relative growth rate, and total biomass (Caldwell et al 2007;Kumari et al 2009;Piri et al 2011;Reddy et al 2013;Bacelar et al 2015;Reyes-Díaz et al 2016;Fina et al (Mhamdi & Breusegem 2018) Note: e --electron; 2H + -2 protons; Fe 2+ -iron divalent ion; t 1/2 -the half-life time; µs -microsecond; ns -nanosecond; ms -millisecond beside a delay in flowering and fruiting (Bassman et al 2003;Reddy et al 2013;Rai & Agrawal 2017). In addition, many studies referred to the negative impact of UV-B on stomatal conductance, which reduces the amount of CO 2 available for photosynthesis (Cechin et al 2007;Lidon et al 2012;Bacelar et al 2015;Cechin et al 2018;Reyes et al 2018;Reyes et al 2019).…”

The effect of different types of mulch and different cultivation methods on the quantitative and qualitative traits of sunflower (Helianthus annuus L.) in Ahvaz climate

“…Sunflower (Helianthus annuus L.) is one of the most valuable oil plant in the world (Cechin et al, 2018) with an oil content of about 25 to 45% (Dhillon et al, 2017).…”